Distinguished human-rights advocates from across the world have released an open letter to the Supreme Court today in which they express concern and chagrin at the possible watering down of legislation that was one of the most important, tangible outcomes of the 1960s U.S. civil rights movement. From Africa, the Americas, Europe, India and elsewhere, the signatories include South Africa’s Archbishop Desmond Tutu, Britain’s leading human-rights advocate Baroness Helena Kennedy, Spanish justice Baltazar Garzón Real, and Sofía Macher, a Peruvian representing Amnesty International. These people have in many instances been decisively inspired by U.S. protection of human rights. Now they say to the justices in Washington, “Beyond your borders, the global march toward justice will suffer grievous harm should you surrender to those who seek to disenfranchise American citizens.”

On November 9, the Supreme Court decided to review Section 5 of the 1965 Voting Rights Act. The law has been essential to battling forces that sought to disenfranchise minority voters. This section requires nine states — Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia, plus scores of counties and municipalities in other states with known histories of racial discrimination — to obtain permission from the Justice Department or a federal court before altering their voting rules.

The case now heading for the highest court in the land, Shelby County v. Holder, was brought by an Alabama county near Birmingham, which argues that Section 5 encroaches unconstitutionally on the sovereign authority of states and that federal appraisal of proposed voting changes, once obligatory to end legal segregation, is no longer required.

The 2012 U.S. national elections were characterized, in the eyes of many observers, by Republican attempts to block voting by minorities and the poor, efforts that have been rejected time and again by federal judges based on the Voting Rights Act, including Section 5. Indeed, Judge John Bates of the federal district court in the District of Columbia rejected a challenge by Shelby County in 2011, noting that when Congress renewed the section in 2006 it found that “40 years has not been a sufficient amount of time to eliminate the vestiges of discrimination.”

The Court of Appeals for the District of Columbia upheld his ruling, indicating that discrimination in voting is “one of the gravest evils that Congress can seek to redress,” while noting that Congress’s careful research in its renewal of Section 5 (22 hearings and 15,000 pages of evidence) “deserves judicial deference.”

Of late, in more than a dozen states, Republican legislators have enacted laws intended specifically to limit citizens’ access to the polls — frequently targeting people in the black and Hispanic communities, students and the poor — not coincidentally groups that strongly turned out in 2008 to elect President Barack Obama. They have enacted strict voter-ID requirements, calculating that millions cannot readily meet them; eliminated early voting; and limited registration drives. (In at least 34 states, voter ID laws have now been introduced.)

The open letter was suggested by Lawrence Guyot, who chaired the Mississippi Freedom Democratic Party, which in 1964 and 1965 led efforts to guarantee the ballot to disenfranchised Mississippians. The alternative party was interracial and formed because the all-white Democratic party in the state would not admit blacks. Guyot, more than any other single human being, did the most to secure the 1965 protection of universal suffrage in the United States. He was a wise and fearless leader who endured numerous severe beatings at the hands of Mississippi law officers. Just before his death in November, he said, “What we must do is to internationalize the continuing fight for the right to vote in the United States.”

Anyone who needs convincing that the shadow of slavery and discrimination still haunts the United States need look no further than the fact that only this month has Mississippi completed ratification of the 13th Amendment to the Constitution, abolishing slavery.